1. Field of the Invention
The present invention relates to a method for driving a plasma display panel (PDP) and more particularly to an alternating current (AC) discharging-type PDP which provides a display in a form of a matrix.
The present application claims priority of Japanese Patent Application No. 2001-052851 filed on Feb. 27, 2001, which is hereby incorporated by reference.
2. Description of the Related Art
A conventional PDP and a method for driving the conventional PDP will be described below by referring to the attached prior art drawings. FIG. 23 is a cross-sectional view showing main portions of the conventional PDP. The conventional PDP includes a front insulating substrate 1a and a rear insulating substrate 1b both being made from glass. On the front insulating substrate la are formed a scanning electrode 2 and a sustaining electrode 3 both being made from transparent conductive material. In order to reduce resistance values of the scanning electrode 2 and the sustaining electrode 3, trace electrode 4 is stacked on each of the scanning electrode 2 and the sustaining electrode 3. A first dielectric layer 9 is formed in a manner that it covers the scanning electrode 2 and the sustaining electrode 3. Moreover, a protecting layer 10 used to protect the first dielectric layer 9 and made from magnesium oxide or a like is formed. On the rear insulating substrate 1b is formed a data electrode 5 extending in a direction orthogonal to the scanning electrode 2 and sustaining electrode 3. Also, a second dielectric layer 11 which covers the data electrode 5 is formed. On the second dielectric layer 11 is formed a rib 7 extending in a same direction as the data electrode 5 extends and is used to partition a discharging cell 12 (FIG. 24) making up a unit portion for displaying in the conventional PDP. On a side face of the rib 7 and on a surface of the second dielectric layer 11 where the rib 7 has not been formed is formed a phosphor layer 8 used to convert ultraviolet rays emitted by a discharge of a discharging gas to visible light. Generally, in a PDP which performs a display in multiple colors, a phosphor layer 8 is formed by putting a necessary phosphor on each region partitioned by ribs to acquire various colors. Therefore, all the phosphor layers 8 corresponding to one piece of the data electrode 5 use phosphors of a same type.
Space being sandwiched between the front insulating substrate 1a and the rear insulating substrate 1b and being partitioned by the rib 7 serves as a discharging space 6 to be filled with helium, neon, xenon, or a like, or their mixed gas. In the conventional PDP being configured as above, a discharge occurs between the scanning electrode 2 and the sustaining electrode 3 (hereinafter the discharge occurring between the scanning electrode 2 and sustaining electrode 3 is referred to as a surface discharge 100).
FIG. 24 is a schematic diagram illustrating an arrangement of electrodes used in the conventional PDP. As shown in FIG. 24, one discharging cell 12 is placed at a point of intersection of one piece of the scanning electrode 2, one piece of the sustaining electrode 3, and one piece of the data electrode 5 which intersects the scanning electrode 2 and the sustaining electrode 3 at right angles. The scanning electrode 2 is connected to a scanning driver integrated circuit (IC) 21 so as to individually apply a scanning voltage pulse. The sustaining electrode 3 is connected to a sustaining circuit 22, in order to provide pulses each having a common waveform, in a manner that all the sustaining electrodes 3 are electrically and commonly connected at an end of a panel or on a driving circuit. The data electrode 5 is connected to a data driver integrated circuit (IC) 23 so as to individually provide a data pulse.
Next, various selective displaying operations of the discharging cell 12 employed in the conventional PDP will be described by referring to FIG. 25. FIG. 25 is a timing chart illustrating a voltage pulse being applied to each electrode (the scanning electrode 2, the sustaining electrode 3 and data electrode 5) in the conventional method for driving the conventional PDP. In FIG. 25, a pre-discharging period A is a period during which a preparation is made to induce an easy discharge in a subsequent selective operation period B. The selective operation period B is a period during which an ON or OFF state of each of the discharging cells 12 for displaying is selected. A discharge sustaining period C is a period during which each of all the selected discharging cells 12 for displaying is discharged. A discharge sustaining terminating period D is a period during which the discharge for displaying is stopped. FIGS. 26A, 26B, 26C, 26D, and 26E show schematic diagrams illustrating a state of a wall charge in the discharging cell 12 during the pre-discharging period A and the selective operation period B in the conventional driving method. Each of states shown in FIGS. 26A to 26E corresponds to a state occurring at each of times t1 to t5 shown in FIG. 25, respectively. Moreover, in the conventional driving method, a reference potential between a pair of electrodes electrically made up of the scanning electrode 2 and the sustaining electrode 3 (hereinafter the pair of electrodes electrically made up of the scanning electrode 2 and the sustaining electrode 3 is referred to as xe2x80x9csurface electrodesxe2x80x9d) is set so as to be a sustaining voltage Vos which is required to sustain the discharge during the discharge sustaining period C. Therefore, a electric potential of the scanning electrode 2 or the sustaining electrode 3 being higher than the sustaining voltage Vos being the reference potential is defined as a electric potential of positive polarity and a electric potential of the scanning electrode 2 or the sustaining electrode 3 being lower than the sustaining voltage Vos being the reference potential as a electric potential of negative polarity. Moreover, a reference potential of the data electrode 5 is set to be 0 (zero) V.
First, during the pre-discharging period A, a sawtooth-shaped pre-discharging pulse Pops having its ultimate potential Vops of positive polarity is applied to the scanning electrode 2 while a rectangular pre-discharging pulse Popc having its electric potential being 0 (zero) V of negative polarity is applied to the sustaining electrode 3. A difference in ultimate potentials between the scanning electrode 2 and sustaining electrode 3 occurring at a time of application of the pre-discharging pulse Pops is a electric potential Vops. The electric potential Vops is set, in advance, at a value exceeding a discharge initiating threshold voltage between the scanning electrode 2 and sustaining electrode 3. A non-disclosed experiment of the inventor of the present invention shows that the discharge initiating threshold voltage between the scanning electrode 2 and sustaining electrode 3 is within a range of 230 V to 250 V and therefore the electric potential Vops is preferably set to be about 300 V. By application of the sawtooth-shaped pre-discharging pulse Pops to the scanning electrode 2 and of the rectangular pre-discharging pulse Popc to the sustaining electrode 3, a voltage of the sawtooth-shaped pre-discharging pulse Pops rises and, from a time point when a voltage between the scanning electrode 2 and the sustaining electrode 3 exceeds the discharging initiating threshold voltage, as shown in FIG. 26A, a feeble surface discharge occurs between the scanning electrode 2 and sustaining electrode 3 (at the time of t1). The feeble surface discharge continues to occur while the electric potential of the sawtooth-shaped pre-discharging pulse Pops is rising, and stops when the electric potential of the sawtooth-shaped pre-discharging pulse Pops has reached the ultimate potential Vops and a change in the electric potential has ended. As a result, as shown in FIG. 26B, a negative wall charge is formed on the scanning electrode 2 and a positive wall charge on the sustaining electrode 3. Moreover, during the pre-discharging period A, the data electrode 5 does not participate directly in the discharge, however, since the electric potential of the data electrode 5 is fixed at 0 (zero) V, as shown in FIG. 26B, some amounts of positive electric charges attracted by an electric field between the scanning electrode 2 and data electrode 5 are adsorbed on the data electrode 5 and, as a result, a feeble positive wall charge is formed on the data electrode 5 (at the time of t2)
Following the application of the pre-discharging pulse Pops, a sawtooth-shaped pre-discharge erasing pulse Pope of negative polarity is applied to the scanning electrode 2. At this point, the electric potential of the sustaining electrode 3 is fixed at the sustaining voltage Vos. As shown in FIG. 26C, when the sawtooth-shaped pre-discharge erasing pulse Pope is applied, the wall charges formed on the scanning electrode 2 and sustaining electrode 3 are erased (at the time of t3). Moreover, even after the wall charges have been erased, in the discharging space 6, a space charge such as an electron, ion, or a like, and activated particle such as metastable particles or a like formed by the pre-discharge still exist. The operation of erasing the wall charge during the pre-discharging period A includes an operation of adjusting the wall charge to have a smooth operation be performed in the subsequent processes such as the selective operations, discharge sustaining operations, or a like.
Next, during the selective operation period B, after the electric potentials of all the scanning electrodes 2 have been held at a base electric potential Vobw once, a scanning pulse Pow of negative polarity having its electric potential being 0 (zero) V is applied to the scanning electrodes 2 and, at the same time, a data pulse Pod which corresponds to a display data and whose electric potential is a electric potential Vod is applied to the data electrode 5. During this period, an auxiliary scanning pulse Posw having its electric potential being Vosw of positive polarity is applied to the sustaining electrode 3. Each of the electric potentials of the scanning pulse Pow and the data pulse Pod is set in a manner that a voltage between a pair of electrodes being electrically made up of the scanning electrode 2 and the data electrode 5 both facing each other (hereinafter the pair of electrodes being electrically made up of the scanning electrode 2 and the data electrode 5 is referred to as xe2x80x9cfacing electrodesxe2x80x9d) does not exceed a discharge initiating threshold voltage between the facing electrodes by application of only either of the scanning pulse Pow or the data pulse Pod and exceeds the discharge initiating threshold voltage between the facing electrodes when the scanning pulse Pow is superimposed on the data pulse Pod. Moreover, a electric potential of a auxiliary scanning pulse Posw is set in a manner that, even when the auxiliary scanning pulse Posw is superimposed on the scanning pulse Pow, a voltage between surface electrodes, that is, between the scanning electrode 2 and sustaining electrode 3 does not exceed a discharge initiating threshold voltage between the surface electrodes. For example, if the discharge initiating voltage between the facing electrodes is 220 V and the voltage Vos of the sustaining pulse Pos is 170 V, a voltage Vow of the scanning pulse Pow can be set to be 0 (zero) V, a voltage Vod of the data pulse Pod can be set to be 70 V and a voltage Vosw of the auxiliary scanning pulse Posw can be set to be Vos+about 20 V.
Therefore, only on the discharging cell in which, in addition of the scanning pulse Pow, the data pulse Pod is applied simultaneously, a discharge occurs between the scanning electrode 2 and the data electrode 5 (at the time of t4) (hereinafter, the discharge occurring between the scanning electrode 2 and the data electrode 5 is referred to as a xe2x80x9cfacing dischargexe2x80x9d). At this point, since there is a electric electric potential difference (Vosw) caused by the scanning pulse Pow and the auxiliary scanning pulse Posw between the scanning electrode 2 and the sustaining electrode 3, a discharge, triggered by the facing discharge between the scanning electrode 2 and data electrode 5, also occurs between the scanning electrode 2 and the sustaining electrode 3. This discharge serves as a writing discharge. Since the space charges and activated particles caused by processes of discharging and erasing wall charges during the pre-discharging period A exist in the discharging space 6, the stable writing discharge can be implemented at a discharge probability based on an amount of the space charge and activated particles. As a result, as shown in FIG. 26E, only in the discharging cell 12 that has been selected in the selective operation period B, positive wall charges are formed on the scanning electrode 2 and negative wall charges are formed on the sustaining electrode 3 (at the time of t5).
Then, during the discharge sustaining period C, the sustaining pulses Pos having crest values being the sustaining voltage Vos and being reversed in phase to each other are applied to all the scanning electrodes 2 and the sustaining electrodes 3. The sustaining voltage is set in a manner that the discharge occurs when the wall voltage formed on the surface electrodes, that is, on the scanning electrode 2 and sustaining electrode 3 by the writing discharge during the selective operation period B is superimposed on the sustaining voltage Vos and that, if there is no superimposition of such wall charges, a voltage for the discharge between the surface electrodes does not exceed the discharge initiating threshold voltage and no discharge occurs. Therefore, only in the discharging cell 12 on which the wall charge is formed by occurrence of the writing discharge during the selective operation period B, the sustaining discharge for displaying occurs.
In the subsequent discharge sustaining terminating period D, the voltage of the sustaining electrode 3 is fixed at the sustaining voltage Vos and a sawtooth discharge sustaining terminating pulse Poe of negative polarity having its ultimate voltage being 0 (zero) V is applied to the scanning electrode 2. This process causes the wall charges on the surface electrodes to be erased and the operation to return back to its initial state, that is, to the state that existed before application of the pre-discharging pulses Pops and Popc during the pre-discharging period A. Moreover, the operation of erasing the wall charge during the discharge sustaining terminating period D includes an operation of adjusting the wall charge to have smooth operations be performed in the subsequent processes.
In the conventional method for actually driving the PDP, each of the periods from the pre-discharging period A or from the selective operation period B to the discharge sustaining terminating period D is defined as one sub-field and a combination of a plurality of sub-fields during which a number of pulses of the sustaining pulse Pos are changed during the discharge sustaining period C with the above sub-fields is defined as one field. Luminance in displaying is adjusted by selecting an ON or OFF state in each sub-field.
Moreover, in the conventional method for driving the PDP, since a probability of occurrence of a discharge induced by the scanning pulse Pow and the data pulse Pod is low, it is better to make a pulse width of the scanning pulse Pow, for example, as long as 10 xcexcs to ensure the selection of the ON or OFF state.
However, actually, because of limitation in time allowable within one field for a television display or a like, a pulse width of the scanning pulse Pow is usually about 3 xcexcs. Therefore, a measure is taken to increase the probability of occurrence of the discharge by raising the electric electric potential Vod of the data pulse Pod. However, an increase in the electric electric potential Vod of the data pulse Vod causes a rise of power consumption. If a pulse width of the scanning pulse Pow is made longer, time of the selective operation period B occupying in one field becomes longer, which inevitably shortens the time of the discharge sustaining period C and, as a result, the number of the sustaining pulses Pos decreases, causing a lowering in luminance.
It has been confirmed from an experiment made by the inventors that, by causing a discharge using the scanning electrode 2 as an anode and the data electrode 5 as a cathode to occur during the pre-charging period A, that is, by causing the discharge of a polarity being opposite to the polarity in the facing discharge using the scanning pulse Pow and the data pulse Pod that is to occur during the selective operation period B to occur during the pre-discharging period A, the probability of the occurrence of the discharge is greatly improved.
However, if the electric electric potential of the scanning electrode 2 is raised while a electric electric potential of the data electrode 5 is fixed, no continuous and feeble discharge occurs and, when the electric electric potential of the scanning electrode 2 exceeds a specified level, a phenomenon in which a strong discharge occurs and then the discharge is temporarily stopped is observed. This is due to an influence of a phosphor layer 8 formed on the data electrode 5. Generally, a secondary electron emission coefficient of the phosphor is lower than that of magnesium oxide (MgO) used as material for the protecting layer 10. Because of this, the discharge using the data electrode 5 as a cathode has a problem in that not only its discharge initiating voltage is made high but also its discharge is difficult to continue in a stable manner.
Moreover, in order to cause the facing discharge to occur, it is necessary to raise the ultimate electric electric potential Vops of the pre-discharging pulse Pops. If the ultimate electric electric potential Vops is set to be higher, in some cases, the discharge occurs also between the scanning electrode 2 and the sustaining electrode 3 during the pre-discharging period A and an amount of the discharge increases. In the PDP, since an increase in the amount of the charges is almost equal to an increase in an amount of emitted light, it causes the increase in the amount of the emitted light during the pre-discharging period A. Luminance at a time when light is emitted during the pre-discharging period A matches luminance at a time when any discharging cell 12 is not selected, that is, luminance occurring at a time of displaying a black color. As a result, this presents a problem in that contrast being one of display characteristics becomes low due to the rise in the luminance in displaying the black color. Another problem is that, since a discharge voltage in the discharge using the data electrode 5 as the cathode is determined by physical properties of the phosphor, in the PDP in which a plurality of kinds of the phosphors is applied in various manners for displaying multiple colors, the discharging characteristic such as the discharge initiating voltage or a like differs in every color to be displayed and therefore its control is made difficult.
In view of the above, it is an object of the present invention to provide a method for driving a PDP capable of improving reliability in selective operations, acquiring excellent displaying characteristics, improving contrast, and accommodating a difference in driving characteristics caused by an emitted color light to be displayed.
According to a first aspect of the present invention, there is provided a method for driving a plasma display panel for causing the plasma display panel, in which a plurality of first electrodes extending in a first direction and a plurality of second electrodes extending in the first direction are placed in such a manner that each of the first electrodes is adjacent to each of the second electrodes and a plurality of third electrodes extending in a second direction orthogonal to the first direction is placed and in which a discharging cell is placed at each point of intersection of each of the first and second electrodes and each of the third electrodes, to perform a display in response to video signals, the method comprising:
a process of causing a discharge to occur between the first electrodes and second electrodes being adjacent to each other in an initializing period; and
a process of causing a discharge of one polarity to occur between the first electrodes and the third electrodes intersecting each other after the discharge between the first electrode and the second electrode starts in the initializing period.
With the above configuration, since the discharge occurs between the first and second electrodes during the initializing period, comparatively large amounts of wall charges are formed on the third electrode. Therefore, a probability of a facing discharge to occur in a subsequent selective discharge is improved.
In the foregoing, a preferable mode is one that wherein includes a process of decreasing intensity of the discharge between the first electrode and second electrode before the discharge of one polarity stops.
Also, a preferable mode is one wherein the process of decreasing intensity of the discharge between the first electrode and second electrode is performed after the discharge of one polarity occurred.
Also, a preferable mode is one wherein the process of decreasing intensity of the discharge between the first electrode and second electrode is performed at a same time when the discharge of one polarity occurs.
Also, a preferable mode is one wherein the process of decreasing intensity of the discharge between the first electrode and second electrode is performed before the discharge of one polarity occurs.
Also, a preferable mode is one wherein the process of causing the discharge of one polarity to occur is started while a space charge is left in a discharging cell.
Also, a preferable mode is one that wherein includes a process of applying sequentially scanning pulses to the first electrode and of causing a selective discharge of opposite polarity between the first and third electrodes by applying a data pulse to the third electrode in response to the video signals.
Also, a preferable mode is one wherein, at a time of causing the selective discharge to occur, wall charges of one polarity are formed on the first electrode and wall charges of opposite polarity are formed on the third electrode and wherein a direction of an electric field being produced by the wall charges in a discharging space matches a direction of an electric field occurring in the discharging space by application of the scanning pulse and the data pulse.
Also, a preferable mode is one wherein the process of causing the discharge between the first and second electrodes to occur includes a process of adjusting timing with which the discharge between the first and second electrodes occurs by calibrating a electric electric potential of the second electrode.
Also, a preferable mode is one wherein the process of causing the discharge of one polarity to occur includes a process of adjusting timing with which the discharge of one polarity occurs by calibrating a electric electric potential of the third electrode.
According to a second aspect of the present invention, there is provided a method for driving a plasma display panel having first and second substrates being placed so as to face each other, a plurality of first electrodes each being placed on a surface facing the second substrate and each extending in a row direction on the first substrate, a plurality of second electrodes each pairing up with the first electrode and extending parallel to the first electrode and making up a display line by a space provided by the adjacent first electrode, and a plurality of third electrodes each being placed on a surface facing the first substrate and extending in a column direction orthogonal to a direction in which the first and second electrodes extend on the second substrate, and operating to have a matrix-type plasma display panel having one discharging cell at each of intersecting points of the first and second electrodes and the third electrode to perform a display in the plasma display panel in response to video signals, the method including:
a process of setting, in a field period making up one screen, at least one initializing period during which a state of the discharging cell is reset, at least one selective operation period during which a selective discharge occurs to select an ON or OFF state for displaying and at least one discharge sustaining period during which a discharge for displaying is achieved, and of causing a discharge to occur, during the initializing period, between the first and second electrodes by applying a pulse whose electric electric potential changes with time to the first electrode; and
a process of causing a discharge of one polarity to occur between the first electrode and third electrode after the discharge between the first electrode and second electrode starts in the initializing period.
In the foregoing, a preferable mode is one that wherein includes a process of sequentially applying a scanning pulse to the first electrode during the selective operation period and of causing the selective discharge of opposite polarity to occur between the first and third electrodes by applying a data pulse to the third electrode in response to the video signals.
Also, a preferable mode is one wherein the discharge of one polarity occurring during the initializing period is a discharge using the first electrode as an anode and the third electrode as a cathode.
Also, a preferable mode is one wherein, at a time of causing the selective discharge to occur, wall charges of one polarity are formed on the first electrode and wall charges of opposite polarity are formed on the third electrode and wherein a direction of an electric field being produced by the wall charges in discharging space matches a direction of an electric field occurring in the discharging space by application of the scanning pulse and the data pulse.
Also, a preferable mode is one that wherein includes a process of decreasing intensity of the discharge between the first electrode and second electrode before the discharge of one polarity stops, during the initializing period.
Also, a preferable mode is one wherein the process of decreasing intensity of the discharge between the first electrode and second electrode is performed after the discharge of one polarity occurred, during the initializing period.
Also, a preferable mode is one wherein the process of decreasing intensity of the discharge between the first electrode and second electrode during the initializing period is performed at a same time when the discharge of one polarity occurs.
Also, a preferable mode is one wherein the process of decreasing intensity of the discharge between the first electrode and second electrode is performed before the discharge of one polarity occurs.
Also, a preferable mode is one wherein the process of causing the discharge of one polarity to occur is started while a space charge is left in the discharging cell, during the initializing period.
Also, a preferable mode is one wherein the process of decreasing intensity of the discharge between the first electrode and second electrode includes a process of decreasing a electric electric potential difference between the first and second electrodes.
Also, a preferable mode is one wherein the process of decreasing the electric electric potential difference between the first and second electrodes includes a process of causing a electric electric potential of the second electrode to come near to a electric electric potential of the first electrode.
Also, a preferable mode is one wherein the process of decreasing a electric electric potential difference between the first and second electrodes includes a process of fixing a difference in electric electric potentials between the first and second electrodes.
Also, a preferable mode is one wherein the process of fixing a difference in electric electric potentials between the first and second electrodes includes a process of matching a change in a electric electric potential of the second electrode to a change in a electric electric potential of the first electrode.
Also, a preferable mode is one wherein the process of fixing a difference in electric electric potentials between the first and second electrodes includes a process of changing a electric electric potential of the third electrode while electric electric potentials of the first and second electrodes are being fixed.
Also, a preferable mode is one wherein the process of decreasing intensity of the discharge between the first electrode and second electrode includes a process of decreasing an increasing rate of a electric electric potential difference between the first and second electrodes.
Also, a preferable mode is one wherein the process of decreasing an increasing rate of a electric electric potential difference between the first and second electrodes includes a process of causing a changing rate of a electric electric potential of the second electrode to come near to a changing rate of a electric electric potential of the first electrode.
Also, a preferable mode is one wherein the process of causing a discharge between the first and second electrodes to occur during the initializing period includes a process of adjusting timing with which a discharge occurs between the first and second electrodes by calibrating a electric electric potential of the second electrode.
Also, a preferable mode is one wherein the process of causing a discharge of one polarity to occur during the initializing period includes a process of adjusting timing with which a discharge of one polarity occurs by calibrating a electric electric potential of the third electrode.
According to a third aspect of the present invention, there is provided a method for driving a plasma display panel having first and second substrates being placed so as to face each other, a plurality of first electrodes each being placed on a surface facing the second substrate and each extending in a row direction on the first substrate, a plurality of second electrodes each pairing up with the first electrode and extending parallel to the first electrode and making up a display line by a space provided by the adjacent first electrode, and a plurality of third electrodes each being placed on a surface facing the first substrate and extending in a column direction orthogonal to a direction in which the first and second electrodes extend on the second substrate and operating to have a matrix-type plasma display panel having one discharging cell at each of intersecting points of the first and second electrodes and the third electrode to perform a display in the plasma display panel in response to video signals, the method including:
a process of setting, in a field period making up one screen, at least one initializing period during which a state of the discharging cell is reset, at least one selective operation period during which a selective discharge occurs to select an ON or OFF state for displaying and one discharge sustaining period during which a discharge for displaying is achieved, and of dividing the plurality of third electrodes into a plurality of electrode groups and holding each of the electrode groups at an individual electric electric potential, during the initializing period; and
a process of causing a discharge between the first and third electrodes to occur.
In the foregoing, a preferable mode is one wherein a plurality of phosphor layers is formed on the third electrode in a manner that the phosphor layer of a same type is assigned to the third electrode of a same type and the third electrode on which the phosphor layer of the same type is formed belongs to the electrode group of a same type.
Also, a preferable mode is one wherein each electric electric potential at which the electrode group is held is set in a manner that a difference in a discharge initiating voltage between the first and third electrodes by a type of each phosphor decreases.
Also, a preferable mode is one that wherein includes a process of causing a discharge between the first and second electrodes to occur before causing a discharge between the first and third electrodes to occur, during the initializing period.
According to a fourth aspect of the present invention, there is provided a method for driving a plasma display panel having first and second substrates being placed so as to face each other, a plurality of first electrodes each being placed on a surface facing the second substrate and each extending in a row direction on the first substrate, a plurality of second electrodes each pairing up with the first electrode and extending parallel to the first electrode and making up a display line by a space provided by the adjacent first electrode, a plurality of third electrodes each being placed on a surface facing the first substrate and extending in a column direction orthogonal to a direction in which the first and second electrodes extend on the second substrate, and a plurality of phosphors formed on the third electrode, and operating to have a matrix-type plasma display panel having one discharging cell at each of intersecting points of the first and second electrodes and the third electrode to perform a display in response to video signals, the method including:
a process of setting, in a field period making up one screen, at least one initializing period during which a state of the discharging cell is reset, at least one selective operation period during which a selective discharge occurs to select an ON or OFF state for displaying and at least one discharge sustaining period during which a discharge for displaying is achieved, and of causing a discharge to occur between the first and second electrodes by application of a pulse whose electric electric potential changes with time to the first electrode during the initializing period;
a process of causing a discharge of one polarity between the first and third electrodes to occur; and
a process of causing intensity of the discharge between the first and second electrodes to decrease before the discharge of one polarity stops.
In the foregoing, a preferable mode is one wherein a process of decreasing intensity of the discharge between the first and second electrodes is performed during a period from a start of a discharge in a discharging cell having a low discharge initiating voltage between the first and third electrodes to a start of a discharge in a discharging cell having a high discharge initiating voltage between the first and third electrodes.
According to a fifth aspect of the present invention, there is provided a method for driving a plasma display panel having first and second substrates being placed so as to face each other, a plurality of first electrodes each being placed on a surface facing the second substrate and each extending in a row direction on the first substrate, a plurality of second electrodes each pairing up with the first electrode and extending parallel to the first electrode and making up a display line by a space provided by the adjacent first electrode, a plurality of third electrodes each being placed on a surface facing the first substrate and extending in a column direction orthogonal to a direction in which the first and second electrodes extend on the second substrate, and dielectric layer to cover the first and second electrodes, and operating to have a matrix-type plasma display panel having one discharging cell at each of intersecting points of the first and second electrodes and the third electrode to perform a display in response to video signals, the method including:
a process of setting, in a field period making up one screen, at least one initializing period during which a state of the discharging cell is reset, at least one selective operation period during which a selective discharge occurs to select an ON or OFF state for displaying and at least one discharge sustaining period during which a discharge for displaying is achieved, and of causing a discharge to occur between the first and second electrodes by application of a pulse whose electric electric potential changes with time to the first electrode during the initializing period; and
a process of causing the second electrode to be a floating electric potential and causing a electric electric potential of the second electrode to match a electric electric potential of the first electrode by capacitive coupling.
In the foregoing, a preferable mode is one wherein a process of matching a change in a electric electric potential of the second electrode to a change of a electric electric potential of the first electrode includes a process of causing the second electrode to be a floating electric potential and causing a electric electric potential of the second electrode to match a electric electric potential of the first electrode by capacitive coupling.
Furthermore, a preferable mode is one wherein the process of causing a changing rate of a electric electric potential of the second electrode to come near to a changing rate of a electric electric potential of the first electrode includes a process of causing the second electrode to be a floating electric potential and causing a electric electric potential of the second electrode to match a electric electric potential of the first electrode by capacitive coupling.
With the above configurations, by causing a stable facing discharge to occur during the pre-discharging period, positive wall charges can be formed on the data electrode. As a result, it is possible to cause a writing discharge to occur at a high probability during a subsequent selective operation period. This is because, during the pre-discharging period, by causing a surface discharge to occur prior to the facing discharge, a stable facing discharge is achieved.
With another configuration, by causing a surface discharge in the pre-discharging period to stop or to be weakened at its middle course, all amounts of the discharge during the pre-discharging period are decreased and luminance in a black display can be lowered, which thus enables improvement of contrast being one of display characteristics of the plasma display panel.
With still another configuration, by applying a voltage being different in every type of a phosphor during the pre-discharging period to the data electrode, a difference in a discharge initiating voltage by a type of the phosphor can be made smaller. This enables an amount of the discharge during the pre-discharging period to decrease as a whole, thus lowering the luminance in the black display and improving contrast in the display of the plasma display panel.